Applied Genetics Inc. has developed a new method for increasing DNA repair in skin by topical delivery of DNA repair enzymes. The specific aim of the Phase I research is to measure the extent and fidelity of the enhanced DNA repair before proceeding to photocarcinogenesis experiments in animals in Phase II. The UV-DNA specific endonuclease V from bacteriophage T4 was introduced into UV-irradiated cells by treatment with endonuclease encapsulated in liposomes and also by gene transfection, resulting in increased DNA repair. Phase I will determine if the enhanced repair is safe and effective in preventing UV mutagenesis. The spontaneous and UV- induced mutation frequency in liposome treated and transfected human cells will be measured. In addition the removal of both pyrimidine and 6-4 photoproducts and the resulting repair patch size will be measured in these cells.